FIG. 1 depicts a conventional magnetic element 10, typically termed a spin valve, that exhibits giant magnetoresistance. The conventional magnetic element 10 includes a seed layer 12, an antiferromagnetic (AFM) layer 14, a pinned layer 16, a conventional spacer layer 24, a conventional oxide layer 26, a pinned layer 28, and a capping layer 34. The pinned layer 16 is a synthetic pinned layer including two ferromagnetic layers 18 and 22 separated by a nonmagnetic conductive spacer layer 20 that is typically Ru. The conventional oxide layer 26 is an oxide of Cu, formed as described below. The conventional free layer 28 includes a bilayer having a CoFe layer 30 and a NiFe layer 32.
FIG. 2 depicts a conventional method 50 for providing the conventional magnetoresistive element 10. FIG. 3 depicts a conventional system 80 for performing at least a portion of the method 50. The system 80 includes a chamber 82, a gas inlet 84 and a pump 86. Also depicted is a wafer 81 on which multiple conventional magnetic elements 10 are fabricated. Referring to FIGS. 2 and 3, the seed layer 12 and AFM layer 14 are provided on the wafer 81, via step 52 and 54, respectively. The pinned layer 16 is formed, via step 56. Step 56 typically includes depositing the ferromagnetic layers 18 and 22 as well as the conductive spacer layer 20. The Cu spacer layer 24 and the conventional oxide layer 26 are fabricated by depositing Cu in step 58 and oxidizing a portion of the Cu in an oxygen atmosphere, via step 60. During the oxidation step 60, oxygen gas is let into the chamber 82 via the gas inlet 84. The flow rate of oxygen gas into the chamber 82 in step 60 is not closely controlled. As a result of the oxidation in step 60, the conventional oxide layer 26 is formed. The free layer 28 is fabricated in step 62. The capping layer 34 is provided, via step 64.
Use of the conventional free layer 28 including a CoFe layer 30 and a NiFe layer 32 allows the conventional magnetic element 10 to have a soft magnetic response and improved signal amplitude, which are desirable for magnetic recording applications. This conventional oxide layer 26 is used also to improve the output amplitude for the conventional magnetic element 10. As a result, the conventional magnetic element 10 may be used in device applications.
Although the method 50 and system 80 are used to configure the magnetic element 10 to have certain properties that are desirable for devices, the magnetic element 10 is subject to serious drawbacks. In particular, the magnetic element 10 may be subject to magnetostriction. Use of the conventional oxidation in step 60 may result in an unstable Fe-oxide phase in the free layer 28. This phase has a large magnetostriction, for example on the order of 3 to 5×10−7. A high magnetostriction adversely affect the stability of a read head (not shown) incorporating the conventional magnetic element 10. Moreover, this magnetostriction is not repeatable over different runs in the apparatus 80. Consequently, the magnetostriction in the free layer 28 may vary widely between conventional magnetic elements 10. Thus, two conventional magnetic elements 10 that are formed using the same method may have significantly different properties. Thus, conventional magnetic elements 10 manufactured using the conventional method 50 and the conventional system 80 may have undesirable magnetostriction that can vary from element to element.
Accordingly, what is needed is a method and system for improving the magnetostriction of magnetic elements. The present invention addresses such a need.